Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Basic set theory question

  1. Oct 3, 2004 #1
    ok, find the intersection of i=1 to infinitie of A(i).

    A(i) = [0, to 1/i].

    I dont understand what it is asking. what do they mean to find the intersection of that?

    and what if A(i) = [0, 1/n)
  2. jcsd
  3. Oct 3, 2004 #2
    To use mathematicasque notation, Intersect[A(i), {i,1,oo}] is the set of all points in each A(i). There's only one point in all A(i)'s: 0. Therefore the intersection is {0}. Same with the second one. But if they made it (0,1/i) then it would be empty.
  4. Oct 3, 2004 #3
    Do you mean:

    [tex]\bigcap_{i=1}^{\infty} A(i)[/tex]

    where A(i) = [0, 1/i]? Wouldn't the answer be {0}?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook